Case reportUrinary bladder carcinoma with divergent differentiation featuring small cell carcinoma, sarcomatoid carcinoma, and liposarcomatous component

Both small cell carcinoma and sarcomatoid carcinoma of the urinary bladder are highly aggressive tumors, and a concurrence of these tumors is extremely rare. We report a case of urinary bladder cancer with small cell carcinoma as a predominant component, accompanied by sarcomatoid carcinoma and conventional urothelial carcinoma (UC). Although the small cell carcinoma component had resolved on receiving chemoradiotherapy, rapid growth of the residual tumor led to a fatal outcome. A 47-year-old man presented with occasional bladder irritation and had a 2-year history of asymptomatic hematuria. Cystoscopy revealed a huge mass in the urinary bladder, and transurethral resection was performed. Microscopically, small cell carcinoma was detected as the major tumor component. Spindle-shaped sarcomatoid cells were also observed that were intermingled with small cell carcinoma and conventional UC. In addition, a sheet-like growth of the lipoblast-like neoplastic cells was observed focally. Initially, by providing chemoradiotherapy, we achieved a marked tumor regression; however, the tumor rapidly regrew after the completion of chemoradiotherapy, and the patient underwent radical cystectomy. Only conventional UC and sarcomatoid carcinoma were identified in the cystectomy specimen. The patient died of the disease 4 months after cystectomy. Urinary bladder cancer may include a combination of multiple aggressive histologies as in the present case. Because the variation in the tumor components may affect the efficacy of therapy, a correct diagnosis of every tumor component is necessary.